Hydraulically operated tools, such as hydraulic hammers for milling stone, concrete, and other materials may be mounted to various machines (e.g., excavators, backhoes, tool carriers, and other types of machines). For example, a hydraulic hammer may be mounted to a boom of a machine and connected to the machine's hydraulic system. High pressure fluid in the hydraulic system may be supplied to the hammer to drive a piston of the hammer in a reciprocating manner. The piston may, in turn, drive a work tool in a reciprocating manner, causing the work tool to break up material it contacts.
Lubrication systems are used to supply lubricant, such as grease, to bearing surfaces in the hydraulically operated tool to reduce friction between moving parts, such as between the tool bit and bushings that are used to align the tool bit. The lubrication system may be separate from the tool, for example by being mounted on a carrier machine, or mounted to the tool, i.e., an on-board system. Whether externally mounted or on-board, a lubricant supply is provided with the system. Operating the tools without lubrication can result in significant damage to the tools. Additionally, allowing air to get trapped in lubrication supply lines when the supply of lubricant runs low or when a cartridge of lubricant or other lubricant reservoir is replaced can result in a requirement to purge the air from the lubrication supply lines and prime the lubricant supply pump before operation of the hammer can continue. In order to monitor the amount of lubricant remaining, many systems provide inspection windows, so that an operator can visually monitor the amount of lubricant remaining. Such systems, however, are dependent on the operator taking the necessary steps to manually check the window, and do not assist with preventing air from becoming entrapped in the lubrication supply lines.
An exemplary lubrication system for a hydraulic hammer is disclosed in U.S. Patent Application Publication No. 2016/0046009 by Moore, published Feb. 18, 2016 (“the '009 publication”). Specifically, the '009 publication discloses a lubrication system for a tool powered by a drive fluid. The lubrication system includes a lubricant charge chamber having a variable volume, a drive fluid valve member, and a detune valve member configured to reduce or limit the amount of pressurized drive fluid being delivered to a piston of the tool. When a low amount of lubricant is detected within a lubricant reservoir from which the lubricant is supplied to the lubricant charge chamber, the tool is derated or detuned.
Although the lubrication system of the '009 publication may be suitable for some applications, it may still be desirable to provide additional features that prevent air from getting trapped in the lubricant supply lines when the pressure of the lubricant drops below a threshold or when additional or replacement sources of lubricant are added to the system. A means for preventing air from being drawn into the lubricant supply lines would eliminate the need to later purge the air and prime the lubricant pumps before continuing operation of the hydraulic tool.
The disclosed system and method are directed to overcoming one or more of the problems set forth above, and/or other problems known in the art.